Engine starter gearing



Feb. 15, 1944.

c. G. ESTEY ENGINE STARTER emmme Filed Nov. 7, 1942 lea lasmvsm'on M A TTORNE 1' Patented Feb. 15, 1944 ENGINE STARTER GEARING Charles G. Estey. Elmira, N. Y., assignor to Bendix Aviation Corporation, South Bend, Ind., a corporation of Delaware Application November 7, 1942, Serial No. 464,873

Claims.

The present invention relates to engine starter gearing, and more particularly to a starter drive of the type which is arranged to hold the pinion in mesh with the engine gear until the engine is reliably self-operative.

A number of starter drives have been developed which maintain the gear connection by virtue of various forms of centrifugal controls. These have been found practical for certain types of engines and operating conditions, but no one type has been found to be adequate for all purposes. Thus, some have proved best for starting engines which are subject to high temperature starting difiiculties such as vapor-lock, while others are particularly adapted to cold weather starting conditions.

It is an object of the present invention to provide a novel starter drive which is arranged to maintain the starting pinion in mesh as long as the cranking circuit is closed until the starting motor has accelerated to substantially its free spinning speed.

It is another object to provide such a device which incorporates a control element that is responsive to acceleration of the starting motor.

It is a further object to provide such a device in which the pinion is held in mesh with the engine gear by a latch which is rendered effective by acceleration of the starting motor due to the relief of the cranking load when the engine starts.

Further objects and advantages will be apparent from the following description taken in connection with the accompanying drawing, in which:

Fig. 1 is a side elevation partly in section of a starter drive embodying a preferred form of the invention;

Fig. 2 is a section taken substantially on the line 2-2 of Fig. 1; and

Fig. 3 is a View similar to Fig. 2 showing the pinion latch in looking position.

In Fig. 1 of the drawing there is illustrated a power shaft l which may be the extended armature shaft of a starting motor not illustrated. A screw shaft 2 is slidably journalled on the power shaft and a pinion 3 is swivelled on the end of the screw shaft for longitudinal movement therewith into and out of engagement with a gear 4 on the engine to be started.

A driving head 5 is fixed on the power shaft in any suitable manner as by means of a cross pin 6 retained by a thimble l. A nut member 8 is threaded on the screw shaft and is provided with r a barrel 9 suitably fixed thereon as by welding or brazing, as indicated at I l. The barrel portion 9 of the nut member 8 extends over a radial flange 12 on the driving head 5, and a lock ring I3 is recessed in the end of the barrel to retain the flange l2 therein.

Means for transmitting rotation from the driving head 5 to the nut member 8 is provided in the form of a yielding driving member [4 of elastically deformable material such as rubber, one end of which rests on the driving head 5 in abutting relation with the flange l2, and the other end engages the side of the threaded portion of nut member 8, the yielding member being retained under slight initial compression by means of lock ring l3.

The idle position of the screw shaft 2 is determined by abutment thereof against the driving head 5 as illustrated, while the operative position thereof isdetermined by a thrust collar IS anchored to the power shaft I in any suitable manher as indicated at l6. An overrunning clutch 11 transmits rotation from the screw shaft 2 to the pinion 3 in a driving direction but permits the pinion to overrun the screw shaft when the engine starts.

According to the present invention means are provided for holding the screw shaft and pinion in meshing position responsive to acceleration of the drive by the starting motor. As here shown, this means is in the form of a weighted latch l8 (Fig. 2) pivoted at I9 to the nut member 8 and having a nose 2| arranged to engage in a notch 22 (Fig. 3) appropriately formed in the screw shaft. A spring 23 fixed in the pivot l9 engages the latch l8 as shown at 24 (Fig. 1) and normally maintains the latch in disengaged position as shown in Fig. 2. When the latch is formed as illustrated with its center of gravity 0 radially outward from the pivot IS, the effect of the spring 23 is augmented by centrifugal force when the drive is in rotation. This is considered the preferable arrangement, but it will be understood that where deemed desirable the latch may be formed with its center of gravity coinciding with its pivotal axis, in which case the latch would not be affected by centrifugal force; or the center of gravity may be located radially inward of the pivotal axis in which case centrifugal force would tend to maintain the engagement of the latch.

In operation, starting with the parts in the positions illustrated in Fig. 1, rotation of the power shaft I by the starting motor is transmitted through the driving head 5 and yielding member l4 to the nut member 8, thereby causing the screw shaft to be traversed longitudinally to mesh the pinion 3 with the engine gear 4. When the longitudinal movement of the screw shaft is stopped by the abutment l5, rotation is transmitted yieldingly to the screw shaft, and through the overrunning clutch I! to the pinion 3 to crank the engine. When the engine starts, the acceleration of the engine gear 4 is transmitted to the pinion 3 causing it to overrun the screw shaft. The release of the cranking load permits the starting motor to accelerate rapidly, and this acceleration causes the latch l8 to tilt into the position shown in Fig. 3 where it engages the notch 22 of the screw shaft. Backward movement of the screw shaft under the dragging effect of the overrunning clutch I! is thus prevented as long as the starting motor continues to accelerate.

If the engine does not remain self-operative, it will quickly slow down to a speed corresponding to the speed of the drive, and the pinion will again transmit rotation to the engine gear. When the engine is reliably self-operative, the operator opens the starting circuit, thus de-energizing the starting motor, whereupon the latch I8 disengages from the screw shaft by reason of the deceleration of the drive assisted by the spring 23, and the screw shaft is returned to idle position by the rotational drag imparted thereto from the pinion by the overrunning clutch IT. The retention of the screw shaft in idle position may be assisted by an anti-drift detent 25 if deemed desirable.

Although but one embodiment of the inven tion has been shown and described in detail, it will be understood that other embodiments are possible and that various changes may be made in the design and arrangement of the parts without departing from the spirit of the invention as defined in the claims appended hereto.

What is claimed is:

1. In an engine starter a power shaft, a pinion mounted thereon for movement into and out of engagement with a gear of an engine to be started, means responsive to acceleration of the power shaft for traversing the pinion into mesh with the engine gear, and means responsive to acceleration of the power shaft for preventin demeshing of the pinion.

2. In an engine starter a power shaft, a pinion mounted thereon for movement into and out of engagement with a gear of an engine to be started, means responsive to acceleration of the power shaft for traversing the pinion into mesh with the engine gear, and means including a latch connected to rotate with the power shaft and movable responsive to acceleration of the power shaft into position to hold the pinion in mesh with the engine gear.

3. An engine starter drive as set forth in claim 2 including further, an overrunning clutch driving connection between the traversing means and the pinion.

4. In an engine starter drive a power shaft, a screw shaft slidably journalled thereon, a nut member threaded on the screw shaft, a yielding driving connection from the shaft to the nut member, a pinion mounted on the screw shaft for longitudinal movement therewith into and out of engagement with a gear of an engine to be started, and means on the nut adapted to engage the screw shaft responsive to acceleration of the nut for preventing longitudinal movement of the screw shaft to demesh the pinion.

5. In an engine starter drive a power shaft, a screw shaft slidably journalled thereon, a nut member threaded on the screw shaft, a yielding driving connection from the shaft to the nut member, a pinion mounted on the screw shaft for longitudinal movement into and out of engagement with a gear of an engine to be started, a latch pivotally mounted on the nut and movable by acceleration of the nut to engage the screw shaft and prevent movement thereof to demesh the pinion, and an overrunning clutch connection between the screw shaft and pinion.

CHARLES G. ESTEY. 

